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Unformatted text preview: ECSE 414 Intro. to Telecom. Networks Assignment #4 - Fall 2009 27/10/10 M. Rabbat ECSE 414 - Homework Assignment #4 Network Layer Due Thursday, November 11, 2009 Note: Unless otherwise noted, all assignments are due at the beginning of the lecture period on the due date. For paper and pencil problems (such as Problems 1, 2, and 3 below), you may submit a hard copy of your assignment in class or to the instructors mailbox, or you can submit your assignment electronically via WebCT. For programming problems (such as Problem 4), you must upload an archive file (e.g., zip, rar, or tgz) on WebCT containing the source code, executable (or .class file for Java applications), and a Readme file containing any special instructions for compiling and running your application. Problem 1 (K&R Ch 4, P30) (4 marks) Consider the count-to-infinity problem in the distance vector routing. Will the count-to-infinity problem occur if we decrease the cost of a link? Why? How about if we connect two nodes which do not have a link? Problem 2 (K&R Ch 4, P43) (4 marks) Consider the operation of the reverse path forwarding (RPF) algorithm in the network shown in Figure 1 below. For this network, find and write down a set of paths from all nodes to the source node A such that if these were the least-cost paths then node B would receive a copy of As broadcast message from nodes A, C, and D under RPF. Figure 1. Network for Problem 2 ECSE 414 Intro. to Telecom. Networks Assignment #4 - Fall 2009 27/10/10 M. Rabbat Problem 3 (10 marks, 5 per part) a) Consider the network topology shown below in Figure 2. Use the distance vector algorithm to calculate forwarding tables at each node. Show your working, including the distance vectors at each node after updates, and the messages that are sent from each node to its neighbors. Do this WITH and WITHOUT poisoned reverse. b) Now consider the situation when the cost of link B-D changes to 40. Use the distance vector algorithm to find the new shortest paths WITHOUT poisoned reverse. Does the count-to- infinity problem exist in this situation? Why or why not? Figure 2: Network for Problem 3. Problem 4: Programming the Distance Vector Algorithm (12 marks) In this assignment you will implement the functionality of a node in a network using a distance vector routing protocol, both with and without poisoned reverse. Download the Java files in hw4prob4.zip. In this problem, you will be filling in or modifying the following files: Node.java template for implementing the functionality of a node in a distance vector network (without poisoned reverse) PoisonedReverseNode.java template for implementing the distance vector algorithm with poisoned reverse; inherits most functionality from Node Hw4Prob4b.java main class to illustrate the effects of using poisoned reverse by recreating the example shown in Figure 4.31b in Kurose & Ross. As given, the template file uses regular Nodes. After implementing a PoisonedReverseNode you will make a minor...
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This note was uploaded on 05/09/2011 for the course ECSE 414 taught by Professor Rabbat during the Fall '10 term at McGill.
- Fall '10